defaults.c

   1 /*
   2  * firewall3 - 3rd OpenWrt UCI firewall implementation
   3  *
   4  *   Copyright (C) 2013 Jo-Philipp Wich <jow@openwrt.org>
   5  *
   6  * Permission to use, copy, modify, and/or distribute this software for any
   7  * purpose with or without fee is hereby granted, provided that the above
   8  * copyright notice and this permission notice appear in all copies.
   9  *
  10  * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
  11  * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
  12  * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
  13  * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
  14  * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
  15  * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
  16  * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
  17  */
  18
  19 #include "defaults.h"
  20
  21
  22 #define C(f, tbl, def, name) \
  23         { FW3_FAMILY_##f, FW3_TABLE_##tbl, FW3_DEFAULT_##def, name }
  24
  25 struct chain {
  26         enum fw3_family family;
  27         enum fw3_table table;
  28         enum fw3_default flag;
  29         const char *name;
  30 };
  31
  32 static const struct chain default_chains[] = {
  33         C(ANY, FILTER, UNSPEC,        "delegate_input"),
  34         C(ANY, FILTER, UNSPEC,        "delegate_output"),
  35         C(ANY, FILTER, UNSPEC,        "delegate_forward"),
  36         C(ANY, FILTER, CUSTOM_CHAINS, "input_rule"),
  37         C(ANY, FILTER, CUSTOM_CHAINS, "output_rule"),
  38         C(ANY, FILTER, CUSTOM_CHAINS, "forwarding_rule"),
  39         C(ANY, FILTER, UNSPEC,        "reject"),
  40         C(ANY, FILTER, SYN_FLOOD,     "syn_flood"),
  41
  42         C(V4,  NAT,    UNSPEC,        "delegate_prerouting"),
  43         C(V4,  NAT,    UNSPEC,        "delegate_postrouting"),
  44         C(V4,  NAT,    CUSTOM_CHAINS, "prerouting_rule"),
  45         C(V4,  NAT,    CUSTOM_CHAINS, "postrouting_rule"),
  46
  47         C(ANY, MANGLE, UNSPEC,        "mssfix"),
  48         C(ANY, RAW,    UNSPEC,        "notrack"),
  49 };
  50
  51 static const struct chain toplevel_rules[] = {
  52         C(ANY, FILTER, UNSPEC,        "INPUT -j delegate_input"),
  53         C(ANY, FILTER, UNSPEC,        "OUTPUT -j delegate_output"),
  54         C(ANY, FILTER, UNSPEC,        "FORWARD -j delegate_forward"),
  55
  56         C(V4,  NAT,    UNSPEC,        "PREROUTING -j delegate_prerouting"),
  57         C(V4,  NAT,    UNSPEC,        "POSTROUTING -j delegate_postrouting"),
  58
  59         C(ANY, MANGLE, UNSPEC,        "FORWARD -j mssfix"),
  60         C(ANY, RAW,    UNSPEC,        "PREROUTING -j notrack"),
  61 };
  62
  63 static struct fw3_option default_opts[] = {
  64         FW3_OPT("input",               target,   defaults, policy_input),
  65         FW3_OPT("forward",             target,   defaults, policy_forward),
  66         FW3_OPT("output",              target,   defaults, policy_output),
  67
  68         FW3_OPT("drop_invalid",        bool,     defaults, drop_invalid),
  69
  70         FW3_OPT("syn_flood",           bool,     defaults, syn_flood),
  71         FW3_OPT("synflood_protect",    bool,     defaults, syn_flood),
  72         FW3_OPT("synflood_rate",       limit,    defaults, syn_flood_rate),
  73         FW3_OPT("synflood_burst",      int,      defaults, syn_flood_rate.burst),
  74
  75         FW3_OPT("tcp_syncookies",      bool,     defaults, tcp_syncookies),
  76         FW3_OPT("tcp_ecn",             bool,     defaults, tcp_ecn),
  77         FW3_OPT("tcp_westwood",        bool,     defaults, tcp_westwood),
  78         FW3_OPT("tcp_window_scaling",  bool,     defaults, tcp_window_scaling),
  79
  80         FW3_OPT("accept_redirects",    bool,     defaults, accept_redirects),
  81         FW3_OPT("accept_source_route", bool,     defaults, accept_source_route),
  82
  83         FW3_OPT("custom_chains",       bool,     defaults, custom_chains),
  84         FW3_OPT("disable_ipv6",        bool,     defaults, disable_ipv6),
  85 };
  86
  87
  88 static bool
  89 print_chains(enum fw3_table table, enum fw3_family family,
  90              const char *fmt, uint16_t flags,
  91              const struct chain *chains, int n)
  92 {
  93         bool rv = false;
  94         const struct chain *c;
  95
  96         for (c = chains; n > 0; c++, n--)
  97         {
  98                 if (!fw3_is_family(c, family))
  99                         continue;
 100
 101                 if (c->table != table)
 102                         continue;
 103
 104                 if ((c->flag != FW3_DEFAULT_UNSPEC) && !hasbit(flags, c->flag))
 105                         continue;
 106
 107                 fw3_pr(fmt, c->name);
 108
 109                 rv = true;
 110         }
 111
 112         return rv;
 113 }
 114
 115 static void
 116 check_policy(struct uci_element *e, enum fw3_target *pol, const char *name)
 117 {
 118         if (*pol == FW3_TARGET_UNSPEC)
 119         {
 120                 warn_elem(e, "has no %s policy specified, defaulting to DROP", name);
 121                 *pol = FW3_TARGET_DROP;
 122         }
 123         else if (*pol > FW3_TARGET_DROP)
 124         {
 125                 warn_elem(e, "has invalid %s policy, defaulting to DROP", name);
 126                 *pol = FW3_TARGET_DROP;
 127         }
 128 }
 129
 130 void
 131 fw3_load_defaults(struct fw3_state *state, struct uci_package *p)
 132 {
 133         struct uci_section *s;
 134         struct uci_element *e;
 135         struct fw3_defaults *defs = &state->defaults;
 136
 137         bool seen = false;
 138
 139         defs->syn_flood_rate.rate  = 25;
 140         defs->syn_flood_rate.burst = 50;
 141         defs->tcp_syncookies       = true;
 142         defs->tcp_window_scaling   = true;
 143         defs->custom_chains        = true;
 144
 145         setbit(defs->flags, FW3_FAMILY_V4);
 146
 147         uci_foreach_element(&p->sections, e)
 148         {
 149                 s = uci_to_section(e);
 150
 151                 if (strcmp(s->type, "defaults"))
 152                         continue;
 153
 154                 if (seen)
 155                 {
 156                         warn_elem(e, "ignoring duplicate section");
 157                         continue;
 158                 }
 159
 160                 fw3_parse_options(&state->defaults,
 161                                   default_opts, ARRAY_SIZE(default_opts), s);
 162
 163                 check_policy(e, &defs->policy_input, "input");
 164                 check_policy(e, &defs->policy_output, "output");
 165                 check_policy(e, &defs->policy_forward, "forward");
 166
 167                 if (!defs->disable_ipv6)
 168                         setbit(defs->flags, FW3_FAMILY_V6);
 169
 170                 if (defs->custom_chains)
 171                         setbit(defs->flags, FW3_DEFAULT_CUSTOM_CHAINS);
 172
 173                 if (defs->syn_flood)
 174                         setbit(defs->flags, FW3_DEFAULT_SYN_FLOOD);
 175         }
 176 }
 177
 178 void
 179 fw3_print_default_chains(enum fw3_table table, enum fw3_family family,
 180                          struct fw3_state *state)
 181 {
 182         struct fw3_defaults *defs = &state->defaults;
 183
 184 #define policy(t) \
 185         ((t == FW3_TARGET_REJECT) ? "DROP" : fw3_flag_names[t])
 186
 187         if (table == FW3_TABLE_FILTER)
 188         {
 189                 fw3_pr(":INPUT %s [0:0]\n", policy(defs->policy_input));
 190                 fw3_pr(":FORWARD %s [0:0]\n", policy(defs->policy_forward));
 191                 fw3_pr(":OUTPUT %s [0:0]\n", policy(defs->policy_output));
 192         }
 193
 194         print_chains(table, family, ":%s - [0:0]\n", defs->flags,
 195                      default_chains, ARRAY_SIZE(default_chains));
 196 }
 197
 198 void
 199 fw3_print_default_head_rules(enum fw3_table table, enum fw3_family family,
 200                              struct fw3_state *state)
 201 {
 202         int i;
 203         struct fw3_defaults *defs = &state->defaults;
 204         const char *chains[] = {
 205                 "input",
 206                 "output",
 207                 "forward",
 208         };
 209
 210         print_chains(table, family, "-A %s\n", 0,
 211                      toplevel_rules, ARRAY_SIZE(toplevel_rules));
 212
 213         switch (table)
 214         {
 215         case FW3_TABLE_FILTER:
 216                 fw3_pr("-A delegate_input -i lo -j ACCEPT\n");
 217                 fw3_pr("-A delegate_output -o lo -j ACCEPT\n");
 218
 219                 if (defs->custom_chains)
 220                 {
 221                         fw3_pr("-A delegate_input -j input_rule\n");
 222                         fw3_pr("-A delegate_output -j output_rule\n");
 223                         fw3_pr("-A delegate_forward -j forwarding_rule\n");
 224                 }
 225
 226                 for (i = 0; i < ARRAY_SIZE(chains); i++)
 227                 {
 228                         fw3_pr("-A delegate_%s -m conntrack --ctstate RELATED,ESTABLISHED "
 229                                "-j ACCEPT\n", chains[i]);
 230
 231                         if (defs->drop_invalid)
 232                         {
 233                                 fw3_pr("-A delegate_%s -m conntrack --ctstate INVALID -j DROP\n",
 234                                        chains[i]);
 235                         }
 236                 }
 237
 238                 if (defs->syn_flood)
 239                 {
 240                         fw3_pr("-A syn_flood -p tcp --syn");
 241                         fw3_format_limit(&defs->syn_flood_rate);
 242                         fw3_pr(" -j RETURN\n");
 243
 244                         fw3_pr("-A syn_flood -j DROP\n");
 245                         fw3_pr("-A delegate_input -p tcp --syn -j syn_flood\n");
 246                 }
 247
 248                 fw3_pr("-A reject -p tcp -j REJECT --reject-with tcp-reset\n");
 249                 fw3_pr("-A reject -j REJECT --reject-with port-unreach\n");
 250
 251                 break;
 252
 253         case FW3_TABLE_NAT:
 254                 if (defs->custom_chains)
 255                 {
 256                         fw3_pr("-A delegate_prerouting -j prerouting_rule\n");
 257                         fw3_pr("-A delegate_postrouting -j postrouting_rule\n");
 258                 }
 259                 break;
 260
 261         default:
 262                 break;
 263         }
 264 }
 265
 266 void
 267 fw3_print_default_tail_rules(enum fw3_table table, enum fw3_family family,
 268                              struct fw3_state *state)
 269 {
 270         struct fw3_defaults *defs = &state->defaults;
 271
 272         if (table != FW3_TABLE_FILTER)
 273                 return;
 274
 275         if (defs->policy_input == FW3_TARGET_REJECT)
 276                 fw3_pr("-A delegate_input -j reject\n");
 277
 278         if (defs->policy_output == FW3_TARGET_REJECT)
 279                 fw3_pr("-A delegate_output -j reject\n");
 280
 281         if (defs->policy_forward == FW3_TARGET_REJECT)
 282                 fw3_pr("-A delegate_forward -j reject\n");
 283 }
 284
 285 static void
 286 reset_policy(enum fw3_table table)
 287 {
 288         if (table != FW3_TABLE_FILTER)
 289                 return;
 290
 291         fw3_pr(":INPUT ACCEPT [0:0]\n");
 292         fw3_pr(":OUTPUT ACCEPT [0:0]\n");
 293         fw3_pr(":FORWARD ACCEPT [0:0]\n");
 294 }
 295
 296 void
 297 fw3_flush_rules(enum fw3_table table, enum fw3_family family,
 298                 bool pass2, struct fw3_state *state)
 299 {
 300         struct fw3_defaults *d = &state->running_defaults;
 301
 302         if (!hasbit(d->flags, family))
 303                 return;
 304
 305         if (!pass2)
 306         {
 307                 reset_policy(table);
 308
 309                 print_chains(table, family, "-D %s\n", state->running_defaults.flags,
 310                                          toplevel_rules, ARRAY_SIZE(toplevel_rules));
 311
 312                 print_chains(table, family, "-F %s\n", state->running_defaults.flags,
 313                                          default_chains, ARRAY_SIZE(default_chains));
 314         }
 315         else
 316         {
 317                 print_chains(table, family, "-X %s\n", state->running_defaults.flags,
 318                                          default_chains, ARRAY_SIZE(default_chains));
 319
 320                 delbit(d->flags, family);
 321         }
 322 }
 323
 324 void
 325 fw3_flush_all(enum fw3_table table)
 326 {
 327         reset_policy(table);
 328
 329         fw3_pr("-F\n");
 330         fw3_pr("-X\n");
 331 }